Arrangement for cooling the rotor of an electric machine, especially a turbine type generator

Abstract

The invention relates to an arrangement for cooling the rotor of an electric machine, especially a turbine-type generator. The rotor contains a superconducting field winding, a co-rotating cold shield and a co-rotating mixing chamber for receiving a phase mixture of a coolant. A first coolant stream with a liquid coolant is further provided for cooling the field winding and a second coolant stream for cooling the cold shield. A substream derived from the first coolant stream after the latter has passed through the field winding is admixed to the second coolant stream and that a corresponding connecting line is provided with a throttling device.

What I claim is: 
     
       1. Apparatus for cooling the rotor of an electric machine having a superconducting field winding longitudinally disposed thereon comprising: (a) a first cold shield exteriorly disposed on and co-rotating with the rotor;   (b) a mixing chamber interiorly and concentrically disposed on and co-rotating with said rotor;   (c) a coolant unit supplying coolant at a low temperature and receiving coolant at a relatively higher temperature;   (d) means for injecting a phase mixture of said coolant of said coolant unit into said mixing chamber via a coolant injecting line;   (e) a first coolant line for a first coolant stream of liquid coolant derived from said coolant phase mixture;   (f) said first coolant line comprising at least one winding feed line radially disposed at one end of said rotor and in communication with said mixing chamber; further a plurality of winding cooling canals interiorly disposed on said rotor and in heat transfer contact with said superconducting field winding, said winding cooling canals being in communication with said winding feed line; and at least one winding discharge line in communication with said winding cooling canals, radially disposed at the other end of said rotor and in communication with said mixing chamber for conducting at least a part of the first coolant stream into said mixing chamber;   (g) a second coolant line for a second coolant stream having at least partly evaporated coolant derived from said coolant phase mixture;   (h) said second coolant line comprising at least one cold shield feed line radially disposed at one end of said rotor and in communication with the radially inner part of the mixing chamber, further at least one cold shield cooling canal in communication with said cold shield feed line said shield cooling canal axially disposed in heat transfer contact with said cold shield; and at least one cold shield discharge line radially disposed at the other end of said rotor, said cold shield discharge line in communication with the input of said coolant unit and said cold shield cooling canal;   (i) a connecting line in communication with said winding discharge line of the first coolant stream and with the cold shield feed or discharge line of the second coolant stream for admixing a coolant substream derived from said first coolant stream after said first coolant stream has passed through said field winding with said second coolant stream; and   (j) a throttling device incorporated within said connecting line whereby the amont of additional coolant fed of the coolant substream into said second coolant stream can be controlled.   
     
     
       2. An apparatus for cooling as recited in claim 1 wherein said coolant injecting line comprises: a central coolant feed line the end of which is formed as an injection nozzle, interiorly positioned on said mixing chamber.   
     
     
       3. An apparatus for cooling as recited in claim 2 wherein the end of said winding discharge line forms a suction canal closely surrounding said injection nozzle whereby the underpressure developing laterally is used to draw up said first coolant stream from said winding discharge line. 
     
     
       4. An apparatus for cooling as recited in claim 1 wherein said mixing chamber is conically shaped, with a smaller cross sectional area at the end of said rotor near said winding discharge line and a larger cross sectional area at the other end of said rotor near said winding feed line. 
     
     
       5. An apparatus for cooling as recited in claim 1 further comprising: a second cold shield interposed between said first cold shield and said rotor;   at least one second cold shield cooling canal interiorly disposed in and in heat transfer contact with said second cold shield, said second cold shield cooling canal being part of said connecting line.   
     
     
       6. An apparatus for cooling as recited in claim 5 wherein said throttling device is interiorly disposed at the end of said second cold shield cooling canal close to the point of communication between said coolant substream and said second coolant stream. 
     
     
       7. An apparatus for cooling as recited in claim 1 further comprising: a plurality of current supply leads in electrical contact with said superconducting field winding;   a second substream derived from said first coolant stream;   means for conducting said second substream to said current supply leads.   
     
     
       8. An apparatus for cooling as recited in claim 7 wherein said second substream is derived from said field winding discharge line. 
     
     
       9. A method for cooling the rotor of an electric machine comprising the steps of: injecting a main coolant stream from a refrigerating means into a mixing chamber within a rotor;   driving said coolant stream into a first stream and a second stream by centrifugal force;   conducting said first stream by centrifugal force of the rotor to a plurality of cooling canals in a field winding;   conducting said second stream through a plurality of cold shield cooling canals and to a refrigerating means;   dividing said first stream into a first substream and a second substream after said first stream has passed through said field winding canals;   conducting said first substream to said cold shield cooling canals and to said refrigeration means;   throttling said first substream to control the flow of coolant;   suctioning said second substream into said main coolant stream.